Hmmm.. I used Bloodshed Dev CPP .. Its the best free C / C++ Ide around IMHO ..
You can also use old versions of Borland's excellent C / CPP Ide ..
Hmm.. I havent seen CPP CDT of Eclipse but Eclipse is a great software for Java .. If it has nice features then try using it ...
Major IT companies may be using VC++ .. .. Or Borland's IDE .. Both cost a bomb ..

However Cygwin project is a separate product offered from a commercial company. Both of them use gcc and compatible binaries and can be used interchangebly. The Windows ports do not scale up to the mark with their Unix counterparts.

Symantec too offers its compilers for free download. But i havent heard anyone use it for commercial purposes.

i had once used bloodshed dev cpp but it does not give any neat (understandable and debuggable) error messages when there is some compilation error.. so i switched back to turbo C++ v3.. which is DOS based .. i once searced on net for some compiler but found all of them paid .. can somebody suggest some link... which is free.. n easy to use.. n not linux based..